The mechanisms that establish cell-specific patterns of neurotransmitter expression are largely unknown. This research will examine (i) the factors that govern the initial expression of particular neuropeptides during embryogenesis; and (ii) the factors that modulate that expression during post-embryonic life. These studies focus on the simple nervous system of the moth in which neurons and their precursor cells are individually identifiable and can be examined with a variety of cellular and molecular approaches throughout their development. In particular, two previously generated monoclonal antibodies recognize cardioactive neuropeptides that are expressed by different identified neurons at various stages of embryonic and postembryonic development. Using these and other cellular and immunological techniques, the potential contributions of cellular environment and invarient cell lineages in directing the fate of these individual peptidergic neurons can be elucidated with great precision. In order to study the developmental regulation of neuropeptide expression in greater molecular detail, the monoclonal antibodies will be used to purify these neuropeptides. Recombinant DNA techniques will then be used to isolate the genes that encode them. Structural information derived from these experiments will facilitate the study of the cell-specific patterns of neuropeptide gene expression in a relatively simple and highly accessible developing central nervous system.